So I've had the unfortunate chance of dealing with brokerages that offer levels. Think Etrade and TD Ameritrade. It's more to protect the brokerage from liability incase you do something stupid. There's a Margin agreement you have to sign to pay for things under Margin. I know its possible to sell premium in cash accounts in the form of full cash Margin covered puts or calls which means you own the 100x shares as specified on option contract its self or have enough buying power since your well capitalized and don't need to sell premium on Margin. Which is what I assume you have over at TD Ameritrade the parent company of Think or Swim a cash accounts. Not Margin approval since you need that to sell premium on Margin. Futures options have SPAN margin you can find this at the CME website. Good luck man also apply for Margin privileges with IB. It's a real brokerage so no Haha. Levels, lmao.
Welcome to the big leagues man.